1. Field of the Invention
The present invention relates generally to a system for eliminating tracking errors in reproducing recorded video signals. More particularly, the invention is directed to a video signal reproducing device using a piezo-ceramic material in the playback head support to compensate for tracking errors.
2. The Prior Art
In video tape recorders video signals are recorded on magnetic tape in a series of parallel magnetic tracks at a predetermined slant angle to the longitudinal direction of the tape. When the tape is run through a playback machine to reproduce the signals, a tracking servo system is employed to make the magnetic head trace, or scan, the recorded tracks correctly. With such a tracking servo system, the rotating speed of a rotary head drum having recording and reproducing heads therein is compared with the longitudinal speed of the tape to generate a signal to control the rotating speed of the rotary head drum, or the longitudinal speed of the magnetic tape, or both. Braking devices are commonly used to control the capstan motor that determines the longitudinal speed of the tape and to control the rate of rotation of the rotary head drum motor. The amount of braking force that must be used makes it necessary to provide a power amplifier to operate the brake devices. This in turn, requires a suitable power source, and the size of the video tape recorder (VTR) must, therefore, be large.
U.S. Pat. No. 3,787,616 describes means for correlating the position of a magnetic playback head longitudinally along a track on which video signals are recorded. The head is supported on a bi-morph leaf that includes piezo-electric sections responsive to control voltages to bend, or deflect, the leaf and thus move the head longitudinally with respect to the track to follow variations in the longitudinal speed of the track. However, the apparatus makes no provision for correction of an error due to a continuing inaccurate speed of the tape which would eventually cause the bi-morph leaf to be bent to its maximum limit, nor does it provide for correction of the tracking of skewed tracks typical of video tape recordings.